The polymeric immunoglobulin receptor (plgR) is expressed in airway epithelial cells and in the serous cells of the submucosal glands. Its normal function is to bind to polymeric immunoglobulins on the basolateral surface and transfer them to the apical surface (the lumen) where they are released, still bound to a portion of the receptor (now called secretory component, or SC) as secretory immunoglobulins. It is specifically adapted to transfer large amounts of cargo across the epithelium, and it is expressed in the cell types in the airway in which the cystic fibrosis transmembrane conductance regulator is also expressed. Thus, from the therapeutic perspective, this receptor is a candidate for two purposes - one, to deliver genes to airway epithelium from the basolateral approach, and two, to ferry therapeutics across the airway from the blood to the lumen. Antibodies have been prepared against this receptor, and a secondary screen requiring them to react with secretory immunoglobulin as well (that is, to bind at a site other than that used by the natural ligand) was applied. These antibodies fall into two categories. One class undergoes rapid transcytosis. The other undergoes rapid uptake, but is retained within the cell in membrane-bounded perinuclear vesicles. This proposal is based on the hypothesis that the "rapid transcytosis" antibodies will produce superior transcytotic therapeutic carriers, whereas the "cell retention" antibodies will be superior for gene transfer, for they will keep their cargo in the cells longer, allowing for escape and nuclear entry. Single chain Fvs will be prepared from representatives of both classes of antibodies and compared for their ability to enhance gene transfer from nonviral gene transfer vectors of compacted DNA, and for their ability to transport, as a fusion protein, a potential therapeutic molecule, 1-antitrypsin, into the airway lumen. Test systems will be both polarized cell lines in culture transfected with the human plgR; human airway epithelial cells grown at the air-liquid interface, which express plgR; and mice transgenic for the human plgR driven by the CC-10 promoter, so that the receptor is expressed only in airway epithelium. If the studies are successful, new therapeutics for cystic fibrosis and other airway diseases can be developed from this base. [unreadable] [unreadable]